Short circuit protection for semiconductor switches

ABSTRACT

Systems, methods, techniques and apparatuses of a semiconductor control system are disclosed. One exemplary embodiment is a method for protecting a semiconductor switch comprising receiving a first voltage during a second blanking period following a first blanking period; determining whether a short circuit fault is occurring by comparing the first voltage to a fast detection threshold corresponding to a first value of a drain-source voltage of the semiconductor switch; if a short circuit is not occurring: receiving a second voltage after the second blanking period ends; determining whether a short circuit fault is occurring by comparing the second voltage to a slow detection threshold corresponding to a second value of the drain-source voltage; and if a short circuit fault is occurring, opening the semiconductor switch, wherein the first value of the drain-source voltage is greater than the second value of the drain-source voltage.

BACKGROUND

The present disclosure relates generally to short circuit protection.Wide bandgap semiconductor switches are becoming increasingly morecommon in power electronic applications such as motor drive units, toname but one example. While wide bandgap switches offer very highswitching frequencies and low switching losses, they are moresusceptible to short circuit currents than other semiconductor switches.For example, many wide bandgap devices only tolerate short circuitcurrents for less than 1 us. Existing semiconductor control circuitssuffer from a number of shortcomings and disadvantages. There remainunmet needs including increasing fault response, reducing short circuitcurrent peaks, and increasing reliability. For instance, conventionalshort circuit detection circuits may delay detection by 2 us or more toavoid false detection. For short circuit faults caused by a load fault,the inductance of the circuit may delay the rise in current enough for aconventional short circuit detection circuit to protect a wide bandgapsemiconductor switch. However, a conventional short circuit detectioncircuit will not respond to low inductance short circuit faults, such asphase leg faults, in time to prevent damage to a wide bandgapsemiconductor switch. Furthermore, the delay added to the detectionprocess allows the current more time to spike, causing stress on anysemiconductor switch when turned off. In view of these and othershortcomings in the art, there is a significant need for the uniqueapparatuses, methods, systems and techniques disclosed herein.

DISCLOSURE OF ILLUSTRATIVE EMBODIMENTS

For the purposes of clearly, concisely and exactly describingnon-limiting exemplary embodiments of the disclosure, the manner andprocess of making and using the same, and to enable the practice, makingand use of the same, reference will now be made to certain exemplaryembodiments, including those illustrated in the figures, and specificlanguage will be used to describe the same. It shall nevertheless beunderstood that no limitation of the scope of the present disclosure isthereby created, and that the present disclosure includes and protectssuch alterations, modifications, and further applications of theexemplary embodiments as would occur to one skilled in the art with thebenefit of the present disclosure.

SUMMARY OF THE DISCLOSURE

Exemplary embodiments of the disclosure include unique systems, methods,techniques and apparatuses for semiconductor switch short circuitprotection. Further embodiments, forms, objects, features, advantages,aspects and benefits of the disclosure shall become apparent from thefollowing description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary process for semiconductor switch shortcircuit protection.

FIGS. 2-4 are graphs illustrating electrical characteristics of asemiconductor switch protected by an exemplary semiconductor controlcircuit.

FIG. 5 illustrates a motor drive including an exemplary semiconductorcontrol circuit.

FIG. 6 illustrates an exemplary semiconductor control circuit portion.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

With reference to FIG. 1, there is illustrated an exemplary process 100for detecting a short circuit fault current flowing through asemiconductor switch while the semiconductor switch is turned on or inthe process of being turned on. Process 100 may be implemented by thesemiconductor control circuits disclosed herein. In certain forms, thephase leg fault detection and load short circuit fault detectionfunctionalities may be performed by separate detection circuits of thesemiconductor control circuits. In certain forms, the phase leg faultdetection and load fault detection functionalities may be performed bythe same detection circuit. It shall be further appreciated that anumber of variations and modifications to process 100 are contemplatedincluding, for example, the omission of one or more aspects of process100, the addition of further conditionals or operations, or thereorganization or separation of operations and conditionals intoseparate processes.

Process 100 begins at operation 101 where a fast fault detection circuitwaits for a first blanking period beginning when a gate driver firstapplies an increasing gate voltage to a gate of the semiconductorswitch. The first blanking period ends when the semiconductor switch isturned on. In certain embodiments, the semiconductor switch isconsidered turned on once the Miller capacitance between the drain andgate of the semiconductor switch is discharged. In certain embodiments,the semiconductor switch is considered turned on once current begins toflow from the drain to the source of the semiconductor switch. Incertain embodiments, the first blanking period is extended by a timeperiod, such as 100 ns or less, after the semiconductor switch is turnedon to increase the accuracy of the determination in operation 105.

In certain embodiments, the semiconductor switch is a wide bandgapdevice, such as a silicon carbide (SiC) switch or a gallium nitride(GaN) switch, to name but a few examples. In certain embodiments, thesemiconductor is an insulated gate bipolar transistors (IGBTs), anotherbipolar semiconductor switch, or another type of silicon basedsemiconductor switch.

Process 100 proceeds to operation 103 where a fast detection circuitreceives a voltage corresponding to the voltage across the drain andsource of the semiconductor switch, also known as a drain-sourcevoltage, during a second blanking period immediately following the firstblanking period. The second blanking period begins once thesemiconductor switch is turned on.

Process 100 proceeds to operation 105 where the fast detection circuitdetermines whether a phase leg short circuit is occurring. The voltagereceived in operation 103 is compared to a fast detection thresholdvoltage. The value of the fast detection threshold voltage correspondsto a value of the drain-source voltage of the semiconductor switch.

In certain embodiments, the fast detection circuit receives a voltagecorresponding to the drain-source voltage during the first blankingperiod instead of waiting during operation 101. The fast detectioncircuit then determines whether a phase leg short circuit fault isoccurring by comparing the received voltage to a third detectionthreshold voltage corresponding to a value of the drain-source voltageof the semiconductor switch. The third detection threshold voltage isgreater than the fast detection threshold voltage. For example, half-waythrough the first blanking period, the fast detection circuit mayreceive a drain-source voltage. If the received drain-source voltage isgreater than 80% of the present blocking voltage of the semiconductorswitch, the fast detection circuit will determine a short circuit faultis occurring and process 100 will proceed to operation 109. In certainembodiments, multiple voltages are received during the first blankingperiod by the fast detection circuit which compares each receivedvoltage to one of multiple threshold voltages, each of the multiplethreshold voltages being less than a previously compared thresholdvoltage but greater than the fast detection threshold voltage.

A phase leg short circuit fault may be a short circuit fault occurringin a drive unit or power electronic device which incorporates thesemiconductor switch. Phase leg short circuits include a low inductancecompared to a load short circuit fault, meaning the rate of change incurrent, instantaneous voltage, and power dissipation are all greaterfor phase leg short circuits than load short circuits. A phase leg shortcircuit fault may be a fault having a current path with an inductanceless than 100 nH, while a load short circuit fault may be a fault havinga current path greater than 200 nH. A phase leg short circuit fault maybe caused by a malfunction of a semiconductor switch, a failure of asemiconductor switch, or an unintentional connection between two pointsin a circuit by a conductive material. A load short circuit fault iscaused by a change in the impedance or resistance of a load that causesload current to increase beyond the rated current capacity of thesystem.

In certain embodiments, the fast detection threshold voltage correspondsto a drain-source voltage of at least 5% of the blocking voltage of thesemiconductor switch, or at least 5 times greater than the slowdetection threshold, as discussed below. In certain embodiments, fastdetection threshold voltage corresponds to a drain-source voltage of atleast 100 V.

Process 100 proceeds to conditional 107. If the fast detection circuitdetermines a phase leg short circuit is occurring, process 100 proceedsto operation 109 where the semiconductor control system responds to thephase leg short circuit fault. In certain embodiments, a gate driver ofthe semiconductor control system responds to a detected fault by openingthe semiconductor switch. In certain embodiments, responding to thephase leg short circuit fault may include transmitting a fault signal toa power converter controller or transmitting an alert to a user. Incertain embodiments, the fast detection circuit determines a phase legshort circuit is occurring within 300 ns of the beginning of the firstblanking period.

In certain embodiments, opening the semiconductor switch occurs within 1us of the beginning of the first blanking period. In certainembodiments, opening the semiconductor switch occurs within 0.25 us ofthe beginning of the first blanking period.

If the fast detection circuit does not determine a phase leg shortcircuit fault is occurring, process 100 proceeds to operation 111 wherea slow detection circuit waits until the second blanking period ends. Insome embodiments, second blanking period may last for a duration of 500ns, to give but one example. While the addition of a second blankingperiod delays the fault response time, the duration of the secondblanking period is configured so as to reduce or eliminate noise, alsoknown as voltage ringing, in the fault detection circuit to preventerroneous fault detection and response. In certain embodiments, thesecond blanking period is longer than the first blanking period. Incertain embodiments, the second blanking period is between 1 us and 2.8us. In certain embodiments, the second blanking period is based onthermal ratings of the semiconductor switch.

Process 100 proceeds from operation 111 to operation 113 where the slowdetection circuit receives a voltage corresponding to the drain-sourcevoltage of the semiconductor switch following the second blankingperiod.

Process 100 proceeds to operation 115 where the slow detection circuitdetermines whether a load short circuit fault is occurring. The voltagereceived in operation 113 is compared to a slow detection thresholdvoltage. The value of the slow detection threshold voltage correspondsto a value of the drain-source voltage of the semiconductor switch. Incertain embodiments, the slow detection threshold voltage corresponds toa drain-source voltage between 5-7V, to name but one example.

Process 100 proceeds to conditional 117. If the slow detection circuitdetermines a load short circuit fault is occurring, process 100 proceedsto operation 109 where the semiconductor control circuit responds to thefault as described above. If the slow detection circuit does notdetermine a load short circuit fault is occurring, process 100 proceedsto end operation 119.

With reference to FIGS. 2-4, there are a plurality of graphsillustrating electrical characteristics of a semiconductor switchprotected by an exemplary semiconductor control system using exemplaryprocess 100 in FIG. 1. The plurality of graphs illustrate electricalcharacteristics during a first blanking period from t₀ to t₁, and asecond blanking period from t₁ to t₂. The plurality of graphs include agate voltage threshold, a fast detection threshold, and a slow detectionthreshold. The gate voltage threshold represents the minimum value ofvoltage applied at the gate of the semiconductor to allow current tobegin to flow through the semiconductor switch. After the gate voltagethreshold is exceeded by the gate voltage, the gate voltage experiencesthe Miller plateau, during which drain-source voltage begins to decreaseand the Miller capacitance discharges. In the illustrated graphs, thesemiconductor switch is considered turned on at the end of the Millerplateau, when the Miller capacitance is fully discharged. The fastdetection threshold is a value of drain-source voltage configured to becompared to the drain-source voltage with the fast detection circuitafter the first blanking period in order to determine a short circuitfault is occurring while avoiding a false fault detection. The slowdetection threshold is a value of drain-source voltage configured to becompared to the drain-source voltage with the slow detection circuitafter the second blanking period in order to determine a short circuitfault is occurring while avoiding a false fault detection.

With reference to FIG. 2, there is a plurality of graphs 200illustrating electrical characteristics of a semiconductor switch duringnominal operation where no short circuit fault is occurring. Theplurality of graphs 200 includes graph 210 illustrating gate voltage,graph 220 illustrating drain-source voltage, and graph 230 illustratingcurrent. Graph 210 includes a line representing gate voltage 211 and agate voltage threshold 213. Graph 220 includes a line representingdrain-source voltage 221, a fast detection voltage threshold 223, and aslow detection threshold 225. Graph 230 includes a line representingcurrent 231 and a nominal current magnitude 233.

At t₀, a gate driver begins to apply an increasing gate voltage 211 tothe semiconductor switch. Once gate voltage 211 exceeds gate voltagethreshold 213, current 231 begins to increase. Once gate voltage 211reaches the Miller plateau, drain-source voltage 221 begins to decrease,and the Miller capacitance begins to discharge. At t₁, the Millercapacitance is fully discharged. After t₁, drain-source voltage 221includes noise causing the drain-source voltage to temporarily exceedslow detection threshold 225. During the period of time between t₁ andt₂, the noise in the drain-source voltage dissipates, and thedrain-source voltage settles under the slow detection threshold 225. Att₂, the second blanking period ends and the drain-source voltage isbelow slow detection threshold 225.

With reference to FIG. 3, there is a plurality of graphs 300illustrating electrical characteristics of a semiconductor switch duringa load short circuit fault. The plurality of graphs 300 includes graph310 illustrating gate voltage, graph 320 illustrating drain-sourcevoltage, and graph 330 illustrating current. Graph 310 includes a linerepresenting gate voltage 311 and a gate voltage threshold 313. Graph320 includes a line representing drain-source voltage 321, a fastdetection threshold 323, and a slow detection voltage threshold 325.Graph 330 includes a line representing current 331 and a nominal currentmagnitude 333.

At t₀, a gate driver begins to apply an increasing gate voltage 311 tothe semiconductor switch. Once gate voltage 311 exceeds gate voltagethreshold 213, current 331 begins to increase. Once gate voltage 311reaches the Miller plateau, drain-source voltage 321 begins to decreaseand the Miller capacitance begins to discharge. Before t₁, drain-sourcevoltage 321 is less than fast detection threshold 323. At t₁, the Millercapacitance is fully discharged. After t₁, drain-source voltage 321includes noise causing drain-source voltage 321 to temporarily exceedthe slow detection threshold 325. During the second blanking period, thenoise in drain-source voltage 321 dissipates, but drain-source voltage321 increases above slow detection threshold 325. At t₂, the secondblanking period ends, drain-source voltage 321 is above slow detectionthreshold 325, and current 331 exceeds the nominal current magnitude333. At t₃, the slow detection circuit determines a load short circuitfault is occurring and opens the semiconductor switch by removing gatevoltage 311 applied to the semiconductor switch gate. In response to theremoval of the gate voltage 311, current 331 decreases to zero.

With reference to FIG. 4, there is a plurality of graphs 400illustrating electrical characteristics of a semiconductor switch duringa phase leg short circuit fault. The plurality of graphs 400 includesgraph 410 illustrating gate voltage, graph 420 illustrating drain-sourcevoltage, and graph 430 illustrating current. Graph 410 includes a linerepresenting gate voltage 411 and a gate voltage threshold 413. Graph420 includes a line representing drain-source voltage 421, a fastdetection threshold 423, and a slow detection voltage threshold 425.Graph 430 includes a line representing current 431 and a nominal currentmagnitude 433.

At t₀, a gate driver begins to apply an increasing gate voltage 411 tothe semiconductor switch. Once gate voltage exceeds gate voltagethreshold 413, current 431 begins to increase. Once gate voltage 413reaches the Miller plateau, drain-source voltage 421 begins to decreaseand the Miller capacitance begins to discharge. At t₁, the Millercapacitance is fully discharged and drain-source voltage 421 exceedsfast detection threshold 423. At t₃, the fast detection circuitdetermines a phase leg short circuit is occurring and opens thesemiconductor switch by removing the gate voltage applied to thesemiconductor gate. In response to the removal of the gate voltage 411,current 431 decreases to zero. At t₂, the second blanking period ends,the fast detection circuit having already responded to the determinedphase leg short circuit fault.

As shown in graph 430, early detection of the phase leg fault during thesecond blanking period by the fast detection circuit enables a softershutdown of the semiconductor switch during the fault response. Bydetecting the phase leg fault early in the second blanking period, thefast detection circuit reduces the thermal stresses of voltagetransients generated by fault current spikes during semiconductor turnoff.

With reference to FIG. 5 there is illustrated an exemplary machinesystem 500 including an exemplary semiconductor control circuit 530. Itshall be appreciated that semiconductor control system 530 may beimplemented in a variety of applications, including low voltage powerconverter systems, medium voltage power converter systems, motor drives,power distribution, and power converters, to name but a few examples.Semiconductor control system 530 is configured to execute an exemplaryshort circuit fault detection process, such as process 100 in FIG. 1. Itshall be appreciated that the topology of system 500 is illustrated forthe purpose of explanation and is not intended as a limitation of thepresent disclosure.

System 500 includes a load 501 coupled to a drive unit 510 structured toconvert power and provide the converted power to load 501. Drive unit510 includes phase leg 520, drive controller 540, and semiconductorcontrol system 530. Phase leg 520 includes semiconductor switches 521and 523 coupled between DC bus 511 at a midpoint connection 525. Load501 is coupled to midpoint connection 525 and structured to receivepower from phase leg 520 by way of midpoint connection 525.

Drive controller 540 is configured to coordinate operation of thesemiconductor switches of drive unit 510 so as provide converted powerto load 501. Drive controller 540 is structured to communicate with agate driver 531 of semiconductor control system 530 and is structured toreceive a fault signal from semiconductor control system 530.

Semiconductor control system 530 is structured to operate semiconductorswitch 523 and protect semiconductor switch 523 from short circuitfaults. In certain embodiments, semiconductor switch 523 includes a widebandgap switch, such as SiC switch or a GaN switch, to name but a fewexamples. In certain embodiments, semiconductor switch 523 includes aninsulated gate bipolar transistors (IGBTs), other bipolar semiconductorswitches, or another type of silicon based semiconductor switch. System530 includes a fast detection circuit 537, a slow detection circuit 533,gate driver 531, and a fault signal generator 535.

Gate driver 531 is structured to selectively provide a gate voltage to agate of semiconductor 523 effective to turn on or turn off semiconductor523 based on instructions or information received from controller 540 orfault signal generator 535. Fast detection circuit 537 is structured todetect a phase leg short circuit fault after the first blanking time.Slow detection circuit 533 is structured to detect a load short circuitfault after the second blanking time. Fault signal generator 535 isstructured to receive a fault signal from circuit 533 or circuit 537,and output a fault signal to gate driver 531 effective to cause gatedriver 531 to open semiconductor 523. Fault signal generator 535 is alsostructured to output a fault signal to drive controller 540 effective tocause controller 540 to stop providing power to load 501. In certainembodiments, one or more of fast detection circuit 537, a slow detectioncircuit 533, and gate driver 531, and a fault signal generator 535 areincorporated into gate driver 531.

It shall be appreciated that any or all of the foregoing features ofsystem 500 may also be present in the other embodiments disclosedherein, such as semiconductor control circuit 600 in FIG. 6.

With reference to FIG. 6, there is illustrated a portion of an exemplarysemiconductor control circuit 600 including fast detection circuit 620,slow detection circuit 610, and fault signal generator 630.Semiconductor control circuit 600 is structured to execute an exemplaryshort circuit fault protection process, such as process 100 in FIG. 1.In certain embodiments, control circuit 600 is configured to respond toa short circuit fault within 1 us using fast detection circuit 620. Incertain embodiments, control circuit 600 is configured to respond to ashort circuit fault within 0.25 us using fast detection circuit 620. Itshall be appreciated that the topology of fast detection circuit 620 andfault signal generator 630 are illustrated for the purpose ofexplanation and is not intended as a limitation of the presentdisclosure.

Circuit 600 is structured to protect semiconductor switch 601 includinga gate 607, a drain terminal 603, and a source terminal 605. In theillustrated embodiment, semiconductor switch 601 is a SiC MOSFET. Inother embodiments, semiconductor switch 601 includes another type ofwide bandgap device or a silicon based semiconductor, such as Si IGBT.

Slow detection circuit 610 may be any type of desaturation circuitconfigured to detect a short circuit fault after the second blankingperiod described above. In certain embodiments, slow detection circuit610 does not detect a short circuit fault until 2 us after the beginningof the first blanking period.

Fast detection circuit 620 is structured to determine a short circuitfault is occurring using a received drain-source voltage. Fast detectioncircuit 620 includes a capacitive voltage divider coupled across thedrain terminal 603 and source terminal 605, the capacitive voltagedivider including capacitors 621 and 622 coupled at a midpointconnection 623. Capacitors 621 and 622 are structured such that thevoltage at midpoint connection 623 corresponds proportionally to thedrain-source voltage across terminals 603 and 605. In certainembodiments, a Zener diode is coupled in parallel with capacitor 622 inorder to protect fast detection circuit 620 from high voltagetransients. In certain embodiments, balancing resistors are coupledacross each of capacitor 621 and capacitor 622 in order to ensure staticvoltage sharing.

A comparator 624 is coupled to midpoint connection 623 and structured toreceive a voltage from midpoint connection 623. Comparator 624 is alsocoupled to a voltage source 625 structured to output a reference voltagecorresponding to a fast detection threshold voltage. Since capacitors621 and 622 are structured to reduce the voltage output to comparator,the reference voltage output by voltage source is also reduced,configured to correspond to a value of the drain-source voltage. Forexample, where the fast detection threshold voltage is 100 V andcapacitors 621 and 622 are structured to reduce the drain-source voltageby a factor of 50, the reference voltage output by voltage source 625 is2 V.

Comparator 624 is structured to compare the voltages received frommidpoint connection 623 and voltage source 625. If the value of thevoltage received from midpoint connection 623 is greater than the valueof the reference voltage received from voltage source 625, comparator624 outputs a high signal to an AND logic gate 626, the high signalindicating the existence of a fault.

AND logic gate 626 also receives input from a delay circuit structuredto delay any output from gate 626 until the first blanking period ends.The delay circuit includes resistor 628 and capacitor 629, bothstructured to receive the gate voltage applied to gate 607. An output ofAND gate 626 is coupled to a latch 627. An output of latch 627 iscoupled to fault signal generator 630.

Fault signal generator 630 includes an OR gate 631 structured to receiveinput from slow detection circuit 610 and latch 627. If either the slowdetection circuit 610 or fast detection circuit 620 determine a shortcircuit fault is occurring, OR gate 631 will receive a high signalinput, causing the OR gate 631 to transmit a fault signal 633 from an ORgate 631 output. The OR gate 631 output may be coupled to the gatedriver for semiconductor switch 601, or a power converter controller fora power converter including semiconductor switch 601. It shall beappreciated that any or all of the foregoing features of circuit 600 mayalso be present in the other semiconductor control circuits disclosedherein.

Further written description of a number of exemplary embodiments shallnow be provided. One embodiment is a method for protecting asemiconductor switch comprising: receiving a first voltage during asecond blanking period following a first blanking period, the firstblanking period beginning when an increasing gate voltage is applied tothe semiconductor switch and ending when the semiconductor switch isturned on; determining whether a short circuit fault is occurring bycomparing the first voltage to a fast detection threshold correspondingto a first value of a drain-source voltage of the semiconductor switch;if it is not determined that a short circuit is occurring: receiving asecond voltage after the second blanking period ends; determiningwhether a short circuit fault is occurring by comparing the secondvoltage to a slow detection threshold corresponding to a second value ofthe drain-source voltage; and if it is determined a short circuit faultis occurring, opening the semiconductor switch, wherein the first valueof the drain-source voltage is greater than the second value of thedrain-source voltage.

In certain forms of the foregoing method, the semiconductor switch is awide bandgap device. In certain forms, opening the semiconductor switchoccurs within 1 us of the beginning of the first blanking period. Incertain forms, the method comprises generating the first voltage using acapacitive voltage divider coupled to a drain of the semiconductorswitch and a source of the semiconductor switch. In certain forms, thefast detection threshold is at least 5% of a blocking voltage of thesemiconductor switch or wherein the fast detection threshold is at leastfive times greater than the slow detection threshold. In certain forms,the method comprises receiving a third voltage during the first blankingperiod; and determining whether a short circuit fault is occurring bycomparing the third voltage to a third detection threshold correspondingto a third value of the drain-source voltage, wherein the third value ofthe drain-source voltage is greater than the first value of thedrain-source voltage. In certain forms, comparing the first voltage to afast detection threshold corresponding to a first value of adrain-source voltage of the semiconductor switch determines whether aphase leg short circuit fault is occurring and comparing the secondvoltage to a slow detection threshold corresponding to a second value ofthe drain-source voltage determines whether a load short circuit isoccurring.

Another exemplary embodiment is a semiconductor control system for asemiconductor switch comprising: a fast detection circuit structured to:receive a first voltage during a second blanking period following afirst blanking period, the first blanking period beginning when anincreasing gate voltage is applied to the semiconductor switch, thefirst blanking period ending when the semiconductor switch is turned on,and determine whether a short circuit fault is occurring by comparingthe first voltage to a fast detection threshold corresponding to a firstvalue of a drain-source voltage of the semiconductor switch; and a slowdetection circuit structured to perform the following if the fastdetection circuit does not determine a short circuit fault is occurring:receive a second voltage after the second blanking period ends;determine whether a short circuit fault is occurring by comparing thesecond voltage to a slow detection threshold corresponding to a secondvalue of the drain-source voltage, wherein the semiconductor controlsystem is structured to open the semiconductor switch in response toeither the fast detection circuit or the slow detection circuitdetermining a short circuit fault is occurring, and wherein the firstvalue of the drain-source voltage is greater than the second value ofthe drain-source voltage.

In certain forms of the foregoing semiconductor control system, thesemiconductor switch is a silicon carbide switch or a gallium nitrideswitch. In certain forms, opening the semiconductor switch occurs within1 us of the beginning of the first blanking period. In certain forms,the fast detection circuit includes a capacitive voltage divider coupledto a drain of the semiconductor switch and a source of the semiconductorswitch. In certain forms, the fast detection threshold is at least 5% ofa blocking voltage of the semiconductor switch. In certain forms, thefast detection threshold is at least five times greater than the slowdetection threshold. In certain forms, the fast detection circuitdetermines whether a phase leg short circuit fault is occurring and theslow detection circuit determines whether a load short circuit isoccurring.

A further exemplary embodiment is a power converter system comprising: asemiconductor switch; a fast detection circuit structured to: during asecond blanking period, receive a first voltage, the second blankingperiod following a first blanking period, the first blanking periodbeginning when an increasing gate voltage is first applied to thesemiconductor switch, the first blanking period ending when thesemiconductor switch is turned on, and determine whether a phase legshort circuit fault is occurring by comparing the first voltage to afast detection threshold corresponding to a first value of adrain-source voltage of the semiconductor switch; and a slow detectioncircuit structured to perform the following if the fast detectioncircuit does not determine a phase leg short circuit fault is occurring:receive a second voltage after the second blanking period ends;determine whether a load short circuit fault is occurring by comparingthe second voltage to a slow detection threshold corresponding to asecond value of the drain-source voltage, wherein the power convertersystem is structured to open the semiconductor switch in response todetermining a phase leg short circuit fault is occurring or a load shortcircuit is occurring, and wherein the first value of the drain-sourcevoltage is greater than the second value of the drain-source voltage.

In certain forms of the foregoing power converter system, thesemiconductor switch is a silicon carbide switch or a gallium nitrideswitch. In certain forms, opening the semiconductor switch occurs within1 us of the beginning of the first blanking period. In certain forms,the fast detection circuit includes a capacitive voltage divider coupledto a drain of the semiconductor switch and a source of the semiconductorswitch. In certain forms, the fast detection threshold is at least 5% ofa blocking voltage of the semiconductor switch. In certain forms, thefast detection threshold is at least five times greater than the slowdetection threshold.

It is contemplated that the various aspects, features, processes, andoperations from the various embodiments may be used in any of the otherembodiments unless expressly stated to the contrary. Certain operationsillustrated may be implemented by a computer including a processingdevice executing a computer program product on a non-transient,computer-readable storage medium, where the computer program productincludes instructions causing the processing device to execute one ormore of the operations, or to issue commands to other devices to executeone or more operations.

While the present disclosure has been illustrated and described indetail in the drawings and foregoing description, the same is to beconsidered as illustrative and not restrictive in character, it beingunderstood that only certain exemplary embodiments have been shown anddescribed, and that all changes and modifications that come within thespirit of the present disclosure are desired to be protected. It shouldbe understood that while the use of words such as “preferable,”“preferably,” “preferred” or “more preferred” utilized in thedescription above indicate that the feature so described may be moredesirable, it nonetheless may not be necessary, and embodiments lackingthe same may be contemplated as within the scope of the presentdisclosure, the scope being defined by the claims that follow. Inreading the claims, it is intended that when words such as “a,” “an,”“at least one,” or “at least one portion” are used there is no intentionto limit the claim to only one item unless specifically stated to thecontrary in the claim. The term “of” may connote an association with, ora connection t₀, another item, as well as a belonging t₀, or aconnection with, the other item as informed by the context in which itis used. The terms “coupled t₀,” “coupled with” and the like includeindirect connection and coupling, and further include but do not requirea direct coupling or connection unless expressly indicated to thecontrary. When the language “at least a portion” and/or “a portion” isused, the item can include a portion and/or the entire item unlessspecifically stated to the contrary.

What is claimed is:
 1. A method for protecting a semiconductor switchcomprising: receiving a first voltage during a second blanking periodfollowing a first blanking period, the first blanking period beginningwhen an increasing gate voltage is applied to the semiconductor switchand ending when the semiconductor switch is turned on; determiningwhether a short circuit fault is occurring by comparing the firstvoltage to a fast detection threshold corresponding to a first value ofa drain-source voltage of the semiconductor switch; if it is notdetermined that a short circuit is occurring: receiving a second voltageafter the second blanking period ends; determining whether a shortcircuit fault is occurring by comparing the second voltage to a slowdetection threshold corresponding to a second value of the drain-sourcevoltage; and if it is determined a short circuit fault is occurring,opening the semiconductor switch, wherein the first value of thedrain-source voltage is greater than the second value of thedrain-source voltage.
 2. The method of claim 1, wherein thesemiconductor switch is a wide bandgap device.
 3. The method of claim 1,wherein opening the semiconductor switch occurs within 1 us of thebeginning of the first blanking period.
 4. The method of claim 1,comprising generating the first voltage using a capacitive voltagedivider coupled to a drain of the semiconductor switch and a source ofthe semiconductor switch.
 5. The method of claim 1, wherein the fastdetection threshold is at least 5% of a blocking voltage of thesemiconductor switch or wherein the fast detection threshold is at leastfive times greater than the slow detection threshold.
 6. The method ofclaim 1, further comprising: receiving a third voltage during the firstblanking period; and determining whether a short circuit fault isoccurring by comparing the third voltage to a third detection thresholdcorresponding to a third value of the drain-source voltage, wherein thethird value of the drain-source voltage is greater than the first valueof the drain-source voltage.
 7. The method of claim 1, wherein comparingthe first voltage to a fast detection threshold corresponding to a firstvalue of a drain-source voltage of the semiconductor switch determineswhether a phase leg short circuit fault is occurring and comparing thesecond voltage to a slow detection threshold corresponding to a secondvalue of the drain-source voltage determines whether a load shortcircuit is occurring.
 8. A semiconductor control system for asemiconductor switch comprising: a fast detection circuit structured to:receive a first voltage during a second blanking period following afirst blanking period, the first blanking period beginning when anincreasing gate voltage is applied to the semiconductor switch, thefirst blanking period ending when the semiconductor switch is turned on,and determine whether a short circuit fault is occurring by comparingthe first voltage to a fast detection threshold corresponding to a firstvalue of a drain-source voltage of the semiconductor switch; and a slowdetection circuit structured to perform the following if the fastdetection circuit does not determine a short circuit fault is occurring:receive a second voltage after the second blanking period ends;determine whether a short circuit fault is occurring by comparing thesecond voltage to a slow detection threshold corresponding to a secondvalue of the drain-source voltage, wherein the semiconductor controlsystem is structured to open the semiconductor switch in response toeither the fast detection circuit or the slow detection circuitdetermining a short circuit fault is occurring, and wherein the firstvalue of the drain-source voltage is greater than the second value ofthe drain-source voltage.
 9. The semiconductor control system of claim8, wherein the semiconductor switch is a silicon carbide switch or agallium nitride switch.
 10. The semiconductor control system of claim 8,wherein opening the semiconductor switch occurs within 1 us of thebeginning of the first blanking period.
 11. The semiconductor controlsystem of claim 8, wherein the fast detection circuit includes acapacitive voltage divider coupled to a drain of the semiconductorswitch and a source of the semiconductor switch.
 12. The semiconductorcontrol system of claim 8, wherein the fast detection threshold is atleast 5% of a blocking voltage of the semiconductor switch.
 13. Thesemiconductor control system of claim 8, wherein the fast detectionthreshold is at least five times greater than the slow detectionthreshold.
 14. The semiconductor control system of claim 8, wherein thefast detection circuit determines whether a phase leg short circuitfault is occurring and the slow detection circuit determines whether aload short circuit is occurring.
 15. A power converter systemcomprising: a semiconductor switch; a fast detection circuit structuredto: during a second blanking period, receive a first voltage, the secondblanking period following a first blanking period, the first blankingperiod beginning when an increasing gate voltage is first applied to thesemiconductor switch, the first blanking period ending when thesemiconductor switch is turned on, and determine whether a phase legshort circuit fault is occurring by comparing the first voltage to afast detection threshold corresponding to a first value of adrain-source voltage of the semiconductor switch; and a slow detectioncircuit structured to perform the following if the fast detectioncircuit does not determine a phase leg short circuit fault is occurring:receive a second voltage after the second blanking period ends;determine whether a load short circuit fault is occurring by comparingthe second voltage to a slow detection threshold corresponding to asecond value of the drain-source voltage, wherein the power convertersystem is structured to open the semiconductor switch in response todetermining a phase leg short circuit fault is occurring or a load shortcircuit is occurring, and wherein the first value of the drain-sourcevoltage is greater than the second value of the drain-source voltage.16. The power converter system of claim 15, wherein the semiconductorswitch is a silicon carbide switch or a gallium nitride switch.
 17. Thepower converter system of claim 15, wherein opening the semiconductorswitch occurs within 1 us of the beginning of the first blanking period.18. The power converter system of claim 15, wherein the fast detectioncircuit includes a capacitive voltage divider coupled to a drain of thesemiconductor switch and a source of the semiconductor switch.
 19. Thepower converter system of claim 15, wherein the fast detection thresholdis at least 5% of a blocking voltage of the semiconductor switch. 20.The semiconductor control system of claim 15, wherein the fast detectionthreshold is at least five times greater than the slow detectionthreshold.